1. Field of the Invention
The present invention relates to a medical instrument used to implant seeds, such as radioactive seeds, into a patient""s body, in order to treat the patient.
2. Description of the Related Art
For treating prostate cancer, radioactive seeds are provided to various locations within a patient""s prostate gland, by way of a medical instrument, also called a seed implantation device. Typically, a base unit which includes an ultrasound unit is used to determine the exact location of the patient""s prostate gland with respect to the base unit. The base unit is capable of being moved either towards the patient or away from the patient.
The ultrasound unit includes a probe, which is inserted into the patient""s rectum while the patient is lying on his back. A grid template is mounted onto the base unit, whereby the grid template includes a plurality of rows and columns of needle holes in which a needle can be inserted. Typically, the grid template includes a 13 by 13 matrix of needle holes, whereby adjacent holes on a row or a column are spaced 5 mm apart. Every other row is labeled with a number (e.g., 1, 2, etc.) on the grid template, and every other column is labeled with an alphabetic character (e.g., A, B, etc.). There is a direct relation between the centerline axis of the ultrasound probe and the position of the holes of the grid template.
Based on information obtained from the ultrasound unit, a needle is positioned through a particular hole (e.g., B5 hole) on the grid template, and then the needle is inserted into a region within the patient""s body in which the prostate gland is located. By using the ultrasound unit, a precise position of the proximal and distal positions (relative to the ultrasound unit) of the prostate gland can be determined and recorded. The distal position (relative to the ultrasound unit) of the prostate gland is also called the xe2x80x9czero retraction pointxe2x80x9d. Once the prostate gland position information is obtained, a seed implantation plan can be determined by a doctor, where the plan corresponds to a sequential process for injecting seeds into particular locations within the patient""s prostate gland. Such treatment is generally started by placing the end of the needle (e.g., bevel end of a bevel needle or the end of a trocar needle) at the zero retraction point, and then start-applying seeds with respect to that reference point.
For a conventional seed implantation device, a needle is first placed into a particular needle hole of a grid template, and then the seed implantation device is held in place by a doctor and attached to the needle. The seed implantation device is then used to inject one or more seeds into the patient""s body through the needle. When finished with that hole, the seed implantation device is detached from the needle, and placed aside. Then, the needle is removed from the grid template, and a new needle is positioned at another needle hole of the grid template, according to the specific plan for treating the patient""s prostate gland. Alternatively, some physicians prefer to insert an entire row of needles onto the grid template, and thereby move from needle to needle. Other physicians implant all needles required at the deepest depth position, and then continue with all needles required at the next-deepest depth position, and so forth. One conventional seed implantation device is called a MICK applicator, and requires the operator to physically reposition the MICK applicator back onto a new needle positioned onto the grid template. Such an applicator is described in U.S. Pat. No. 5,860,909, entitled Seed Applicator for Use in Radiation Therapy.
The MICK applicator is manually moved by the operator between seed implant locations. This results in inaccuracies due to the operator not being capable of precisely retracting the medical instrument to a next seed implant position, due to human error and the size and weight of the medical instrument.
The present invention is directed to a medical instrument, which provides for precise indexing between seed implant locations.
According to one aspect of the invention, the medical instrument includes means for affixing to another device to obtain a reference position. The medical instrument also includes means for automatically indexing the medical instrument with respect to the reference position.
According to another aspect of the invention, the medical instrument includes an attachment device for attachment to a sheath nit of a targeting fixture. The medical instrument also includes an indexing unit for indexing the medical instrument relative to the sheath unit, in order to move the medical instrument relative to a patient to be treated by way of the medical instrument.